energy transfer & resources

Created by

Iris Campbell

Cards (70)

Heat transfer is the transfer of energy from a hot object to cooler objects or surroundings.
Conduction is the transfer of energy through the collision of particles
metals are the best conducting solids as their particles are close together and they have free moving electrons between their atoms
liquids and gases are poor conductors because the particles are further apart than solids and cannot pass on vibrations as easily
how does a solid conduct?
particles gain kinetic energy
particles vibrate and pass on vibrations to neighbouring particles
process continues until all particles are vibrating, causing temperature to increase
how does a metal conduct?
free electrons gain kinetic energy
these move between metal atoms & collide with them
causes metal atoms to vibrate with more kinetic energy
these cause neighbouring atoms to vibrate, causing temperature to increase
convection currents are currents of moving liquids or gases transferring energy
convection in a fluid
liquid particles gain kinetic energy
move further apart
fluid expands, becomes less dense and rises
hotter & less dense fluid now rises above denser fluid
as it rises, the fluid loses kinetic energy and sinks
process continues and causes more kinetic energy to be transferred to the fluid each time
how is the earth warmed?
thermal energy emitted through the sun travels through space in the form of infra-red radiation
some of this radiation is absorbed & warms the earth, and some of it is reflected back to space
the leslie cube demonstrates how dark dull objects are the best emitters and absorbers of radiation
insulation and lubrication can prevent thermal energy transfer
an insulator traps air and stops particles moving & therefore prevents conduction and convection
types of energy stores
chemical, kinetic, gravitational, elastic, thermal, magnetic, electrostatic, nuclear
types of energy transfer
mechanically, electrically, by heating, by radiation
energy is the capacity to do useful work measured in joules (J)
energy cannot be created or destroyed, only transferred from one form to another
potential energies can be released into other forms
efficiency = useful energy input / total output x 100
efficiency is a measure of how much total input energy is usefully transferred
if efficiency is given as a percentage, divide by 100 before using the formula triangle
sankey diagrams represent energy transfer. thicker arrows represent more energy transferred
work done (J) = force (N) x distance moved (M)
work done is equal to energy transferred
power = work done / time taken
two main waste products of fossil fuels are carbon dioxide and carbon monoxide, which are greenhouse gases causing global warming
kinetic energy = 1/2 x mass x velocity^2
an object which is moving has kinetic energy
gravitational potential energy (GPE) = mass x gravitational field strength x height
an object above ground level has stored GPE
it is measured in joules
work done = force x distance moved
work done is equal to energy transferred when moving an object
their formula is therefore the same
work done is measured in joules
gravitational potential energy = mass x gravitational field strength x height
kinetic energy = 1/2 x mass x speed squared
loss in gravitational potential energy = gain in kinetic energy
GPE lost (J) = KE gained (J)
the gravitational force of earth is 10
the conservation of energy produces a link between GPE, kinetic energy & work
eg when a ball is dropped, gravity does work on it & its GPE becomes kinetic energy as it accelerates downwards
therefore work done is equal to GPE
energy can be transferred in heating through radiation, convection or conduction
thermal radiation is the transfer of energy by heating by infrared electromagnetic waves
conduction and convection are energy transfers that involve the transfer of energy by particles
conduction is the main form of energy transfer by heating in solids
convection is the main form of energy transfer by heating in liquids and gases